MST

[Brad_199]

Operating rules state:

all switches in a region must be configured with the same set of VLANs

all switches in a region must have the same VID-to-MST instance assignment

I've setup a single region with 5 switches and 1 of those switches has a different set of VLAN's to the remaining 4 - how was that possible then?

In a two tier hierachy (core + access layer) surely it isn't uncommon to have the core switch(es) include a different set of VLAN's (for infrastructure devices) than the access layer with client/end user devices.

How can you make that work when a single MST region is supposed to need all switches in the region to have the same instance mapping??

[Richard Brodie_1]

The second rule is the important one: an MD5 digest of the mapping is taken, and they need to be the same for switches in the same region. show span mst-config should look the same on each switch. If they aren't then I'd be sceptical that they really are in the same region.

More recent/higher end firmware allows the mappings to be created, even if the VLAN isn't configured on the switch, and that is sufficient. Even without that feature, nothing says  that the trunks between the core and the access layer have to carry all the VLANs.

[Brad_199]

I see.

There is no requirement to extend some of the core VLAN's onto the access layer so you propose that I just create the same instance mapping on all access layer switches regardless?

All switches have latest firmware.

[Richard Brodie_1]

There is no requirement to extend some of the core VLAN's onto the access layer so you propose that I just create the same instance mapping on all access layer switches regardless?

If you want them in the same region, yes.